The human eye is a complex sensory organ composed of a cornea, which refracts light on route to the pupil, an iris which controls the size of the pupil thus regulating the amount of light entering the eye, and a lens which focuses the incoming light through the vitreous fluid to the retina. The retina converts the incoming light into electrical energy that is transmitted through the brain stem to the occipital cortex resulting in a visual image.
As the body ages, the effects of oxidative damage contributes to a loss of lens flexibility and the accumulation of denatured proteins that slowly coagulate reducing lens transparency. The natural flexibility of the lens is essential for focusing light onto the retina by a process referred to as accommodation. Accommodation allows the eye to automatically adjust the field of vision for objects at different distances. In general, most accommodation is lost by the age of 50, and this condition is known as presbyopia. Presbyopia usually begins to occur in adults during their mid-forties and mild forms can be treated with glasses or contact lenses.
Lenticular cataract is a lens disorder resulting from the development of coagulated protein and calcification. There are four common types of cataracts: senile cataracts associated with aging, traumatic cataracts which develop after a foreign body enters the lens capsule or following intense exposure to ionizing radiation or infrared rays, complicated cataracts which are secondary to diseases such as diabetes mellitus or eye disorders such as detached retinas, glaucoma and retinitis pigmentosa, and toxic cataracts resulting from medicinal or chemical toxicity. Regardless of the cause, the disease results in impaired vision and may lead to blindness.
Treatment of severe lens disease often requires the surgical removal of the natural lens. Modern surgery involves phacoemulsification, followed by irrigation and aspiration, which removes the lens cortex and nucleus while leaving the lens capsule. An artificial intraocular lens is then inserted into the lens capsule or the anterior chamber to restore vision. Present IOLs have elastomeric characteristics and are designed for small incision implantation. The lenses are typically rolled or folded, inserted into the lens capsule and then unfolded once inside.
To reduce surgical incisions to 1.5 mm or less, some scientists have looked to the development of injectable IOLs in which a polymer lens composition is injected into an empty lens capsule and cured in-situ as a part of the surgical procedure. Essentially, the cured lens will assume the shape of the lens capsule. Alternatively, it has been proposed that one can insert a thin-walled inflatable balloon of silicone rubber into an empty lens capsule. The lens composition is then injected into the balloon and assumes the pre-determined shape of the balloon, presumably to provide greater shape control and containment of the lens composition.
There have been several attempts to develop materials suitable for use as injectable IOLs. For example, Gerace et al. describe a fast curing mixture of vinyl-containing polyorganosiloxane, organosilicone comprising hydride groups and a platinum group metal catalyst in U.S. Pat. Nos. 5,278,258, 5,391,590 ('590) and U.S. Pat. No. 5,411,553. See also, U.S. Pat. Nos. 6,613,343 and 6,737,496 to Hodd et al.
Kelman describes an injectable collagen material in U.S. Pat. No. 5,476,515. The material is said to be clear, resistant to epithelialation and capable of accommodation. The material is prepared from a transparent collagen compound that has a refractive index range from 1.2 to 1.6. The collagen compound is injected into an empty lens capsule.